1. Field of the Invention
This invention relates to an acrylic polymer dispersant useful for preparing pigment dispersions for aqueous acrylic coating compositions.
2. Description of the Prior Art
Aqueous acrylic coating compositions are well-known in the art. However, there has been a problem of incorporating pigments into these aqueous compositions, particularly iron oxide pigments which are very difficult to disperse in these aqueous coating compositions. Backhouse et al. U.S. Pat. No. 3,723,151, issued Mar. 27, 1973, is directed to a dispersant containing aromatic groups used for organic liquids but not for aqueous coating compositions. Fuch et al., U.S. Pat. 3,752,688, issued Aug. 14, 1973, is directed to a process for grinding a select group of pigments in an aqueous alkaline medium then the resulting dispersion is used in lacquers and varnishes. British Pat. No. 1,123,303, published Aug. 14, 1968, is directed to dispersants of acrylic imine-modified carboxylic polymers in which the carboxyl groups have been reacted with an alkaline imine. The dispersants disclosed in the art are useful for solvent-based coating compositions rather than aqueous acrylic coating compositions. The art does not provide for a dispersant that can be used with all types of pigments in aqueous acrylic coating compositions.